First Record of Xenocyon Lycaonoides from the Early Pleistocene of the Gonghe Basin, Tibetan Plateau, and Its Biogeographic Implications

Xenocyon lycaonoides was a large and hypercarnivorous canid that was widely distributed across Eurasia and North America during the Pleistocene. Here we describe a partial mandible of Xenocyon collected from the Early Pleistocene strata (1.77–1.95 Ma B.P.) of the Gonghe Basin, Qinghai Province, China, representing the oldest record of this species. Morphological analysis reveals that the specimen is characterized by a remarkably large anterior mental foramen, an extremely reduced m1 entoconid and the absence of the m1 medial ridge of the hypoconid. These features distinctly distinguish the material from the other hypercarnivorous taxa such as Lycaon and Cuon, justifying its referral to Xenocyon lycaonoides. The Gonghe specimen possesses a more slender mandible and slender molars than those of the chronologically younger population of this species, reflecting an evolutionary trend toward increased bite force and adaptation to larger prey. This discovery of the oldest record of X. lycaonoides in the Tibetan Platea suggests that the Tibetan Plateau likely served as a significant geographic unit for the origin and early diversification of this lineage. With the development of open grassland environments during the Early Pleistocene, Xenocyon lycaonoidesexperienced rapid dispersal and range expansion.